Critical tension crack depth in rockslides that conform to the three-section mechanism
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Guoqing Chen I Peng Tang I Runqiu Huang I Dong Wang I Zhiheng Lin I Da Huang
Critical tension crack depth in rockslides that conform to the three-section mechanism
Abstract The three-section mechanism is a typical mechanism of large-scale rockslides. Such rockslides are typically characterized by sudden instability and can cause many casualties and considerable economic losses due to their high-speed and long-distance runout. Their evolutionary process is closely related to the development of the tension crack at the trailing edge and the sudden brittle failure of the locked section. In this study, the curved failure path of the locked section was verified by means of the numerical simulation conducted using PFC2D. On the basis of that, the critical threshold of the tension crack depth for slope instability was derived based on the limit equilibrium state determined using the vector sum method, and this threshold was then verified through application in a case study. The results show that the critical tension crack depth threshold is not only related to the slope height but also closely related to other geometric and mechanical parameters of the slope. In addition, the case study shows that the result calculated using the methodology proposed in this paper is more accurate than that obtained from the previous empirical equation. Hence, the outcomes of this study are significant for improving stability analyses, instability prediction, and the early warning of instability for such rockslides. Keywords Rockslides . Three-section mechanism . Tension crack . Critical depth . Instability prediction and early warning Introduction The three-section mechanism is the underlying mechanism of a typical geomechanical model for large-scale rockslides. In this model, the sliding surface is directly determined by three sections (Fig. 1): (a) the creep section along the weaker strata, (b) the steep tension section along the tension crack at the rear, and (c) the curved locked section in between (Huang 2009; Huang 2012). During the evolution of such a rockslide, the sliding at the slope toe driven by continuous creep deformation causes the initiation of a tension crack from the head of the slope that then propagates farther into the body of the slope until shear failure of the locked section occurs. Evidently, the evolutionary process of this type of rockslide is closely related to the development of the tension crack at the trailing edge; hence, this crack development is a vital concern for real-time monitoring and early warning. Since these rockslides typically occur suddenly, as determined by the brittle shear failure of the locked section when the tension crack reaches a certain depth, the high-speed and long-distance runout of such a rockslide usually results in many casualties and considerable economic losses (Zhang and Liu 1990; Huang et al. 1991; Huang and Deng 1993; Sartori et al. 2003; Eberhardta et al. 2004). For a rockslide that conforms to the three-section mechanism, the instability of the slope is almost impossible
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